NYC-WTC_000199886

NYC 9/11 Public Portal Document

• December 2: first floor hall by exit 1; second floor hall by exit 1; third floor hall by exit 1; roof.

The results of this sampling are as follows;

• Metals: The results of the metals analyses showed that most metals were not detected either inside or outside of the school in any of the samples. Chromium was detected at trace levels in all samples but at similar levels to the method blank. Traces of iron were detected in two of the samples.

• Hydrocarbons; The results of the hydrocarbon analyses showed that most samples had low to non-detectable levels of most of the hydrocarbon compounds that were tested, although most samples also showed some level of undifferentiated hydrocarbons, which could represent a material such as mineral spirits. A few hydrocarbon compounds were detected in one or two sample each at concentrations above the method detection limit, including xylenes (maximum concentration of 0.294 ppm), ethylbenzene (0.154 ppm), tetrachloroethene (0.346 ppm), and chlorobenzene (0.129). There was extensive painting being conducted inside the school during the sampling period, as well as cleaning. The targeted hydrocarbon compounds detected in a few samples, which included ethylbenzene and toluene, are often present in certain paints or products used in painting. It is significant to note that the samples collected on December 2 contained no specific hydrocarbon compounds and only trace levels of unspecified hydrocarbon compounds. It is stated in the ATC report that the paint odors, which had been strong inside the school during the earlier sampling dates, had largely dissipated by December 2. Follow-up sampling for hydrocarbons and other volatile organic compounds is discussed later.

• Particulates and Other Air Quality Parameters: Levels of carbon dioxide, carbon monoxide, and relative humidity were within guideline ranges. Levels of particulates (PM2.5) varied significantly during the period and appeared to generally correlate with outdoor levels. On one of the days, November 30, the particulate levels also exceeded the 65 ug/m^ standard for normal populations. It should be noted that 65 ug/m^ limit is established for outdoor conditions as an average concentration over 24 hours. On three of the four dates, some particulate measurements exceeded the guidance level of 40 ug/m^ established by USEPA for sensitive receptors. It should be noted that there has been some discussion that the method used to measure particulate levels may register higher particulate levels than would be measured by performing a gravimetric analysis of total particulates. ENVIRON has requested that the Board of Education’s consultant perform a comparative analyses using the particulate meter and gravimetric analysis to determine the comparability between the two methods. The results of that comparison has not yet been received.

3

CITY_21MC100_008972439

NYC-WTC_000199888